Field of the Invention
The present invention relates to a method and apparatus for controlling restart of a vehicle equipped with an idle stop and go (ISG) Auto Hold system, and more particularly, to a method and apparatus for controlling restart of a vehicle equipped with an ISG-Auto Hold system, which allows drivers to operate the vehicle instantaneously to reduce risk of accident.
Description of the Related Art
Vehicles that have been launching recently are equipped with an engine to which an ISG system is applied to improve fuel efficiency and reduce emissions. The ISG system is an engine control system that shuts off the engine automatically, which is referred to “Idle Stop,” when the driver engages a brake pedal under an idle state of the engine, and then turns on the engine automatically for the vehicle to run normally, which is referred to “Go,” when the driver engages an accelerator pedal and thereby an engine restart request by the driver's intention occurs.
In general, ISG entry condition for shutting off the engine includes engagement of the brake pedal under the standstill state when no vehicle speed is detected (e.g., the vehicle speed is 0). When such an ISG entry condition is fulfilled, control for shutting off the engine is performed by stopping fuel supply and ignition. Further, when the driver's request for restarting the engine (i.e., request for starting the vehicle) such as operation of an accelerator pedal, release of a brake pedal, operation of a clutch pedal and the like is detected, control for restarting the engine, which turns on the engine again for the vehicle to run normally, is performed. Vehicles equipped with this ISG system may achieve the effect of increasing fuel efficiency by about 5 to 15%.
In addition, an Auto Hold system that is often mounted on vehicles having been launched recently is referred to a type of convenient system for securing driver's driving convenience and safety of driving, which eliminates inconvenience that the driver must continuously engage a brake pedal by maintaining pressure on the brake pedal while the vehicle stops. When the brake pedal is depressed or engaged in drive range (D range) and then the vehicle stops, a brake sensor is configured to detect the pedal engagement and transmit a signal corresponding thereto to a controller, and the controller is configured to actuate a solenoid valve in response to the signal to maintain hydraulic pressure of a master cylinder, and thus, the vehicle maintain the engagement of the brake pedal even when the driver releases the brake pedal after few seconds.
Accordingly, the Auto Hold system has an advantage in that it allows the driver's foot to relax by maintaining brake pressure and allows the vehicle to restart without rolling backward on an uphill road or a heavy slope way. It follows that the brake pressure of the vehicle is maintained by operation of the Auto Hold system, and then the brake pressure is released automatically when the accelerator pedal is depressed.
In vehicles equipped with both an ISG system and an Auto Hold system (hereinafter, the “vehicle equipped with an ISG-Auto Hold system”), when the brake pedal is depressed under an idle state, the engine is shut off by the ISG and the vehicle is maintained stationary by the Auto Hold. Thereafter, when the accelerator pedal is depressed, the Auto Hold is released and the engine is turned on, to thus improve functions driver's convenience and fuel efficiency may be improved.
In vehicles equipped with a conventional ISG-Auto Hold system as described above, the ISG maintains the engine turned on when the vehicle maintains the engagement of the brake pedal (i.e., state that the Auto Hold is turned on), or when the vehicle is under running (i.e., state that the Auto Hold is turned off and an opening degree rate of an accelerator pedal is greater than 0%), while the ISG forces the engine to turn off when the above conditions are not fulfilled. In other words, the state that the Auto Hold is turned on is a safe state, while the state that the Auto Hold is turned off and the opening degree rate of the accelerator pedal is greater than 0% is a relatively safe state since the driver has an intention to drive the vehicle. Therefore, restarting is permitted only under the safe state as described above.
Further, when the opening degree rate of the accelerator pedal is 0% (e.g., the pedal is disengaged) under the state that a drive gear is input (D range) and the Auto Hold is turned off, it is a state that the driver is looking at another place, not towards the front of the vehicle (e.g., situation that the driver is looking at a rear seat). Accordingly, when the engine is turned on, an accident may occur due to the forward movement of the vehicle. Therefore, to avoid such a situation, when the driver has no intention to drive the vehicle (i.e., if the opening degree rate of the accelerator pedal is 0%), the engine may be forcedly turned off.
However, in vehicles equipped with such conventional ISG-Auto Hold system as mentioned above, when the driver slightly steps on the accelerator pedal (e.g., an initial engagement of the pedal) and immediately releases the accelerator pedal under the state that the engine is turned off and the vehicle is maintained stationary by operation of the Auto Hold and ISG, various problems may occur. In other words, when the accelerator pedal is depressed slightly, the Auto Hold may be released. However, when the accelerator pedal is released immediately after depressing the accelerator pedal, the opening degree rate of the accelerator pedal is 0% and thus, the engine will not be restarted by the ISG system. In particular, the driver expects that the engine has been restarted, but the engine has not been restarted differently from the driver's expectation. Accordingly, there have been problems that since the driver cannot perform an instantaneous control to the vehicle, discomfort of the driver is weighted and risk of accident is increased.